Make the surroundings murky, gloomy, nebulous, and muggy. Let there be darkness. A huge lawn attached to the house with dead plants in it. Let the crickets make it their haven. Broken windows, moss covered walls, a leaning antenna at the top and a dim light from a single bulb (out of all the windows in the mansion, just the one window has the bulb) makes a building spine chilling!
Fill it with clowns! I did a student film shoot a long time ago at a place that had been an orphanage, but was in the middle of being bought, flattened and turned into a corporate banking office. There was a power cut halfway through the all night shoot and lucky me got to go downstairs to check the mains. When I got downstairs, I couldn't find the box, but there was what looked like a full chapel underground, complete with long wooden pews and a pulpit. No one went downstairs to confirm what was there, because the power came back. I still don't know why there was a chapel under this massive, mostly above ground building- perhaps there is a perfectly good reason. Nothing weird happened, I didn't hear any voices or see anything move, but walking between those pews in the dark was one of the scariest, purely building related experiences of my life.
Dilapidation, previous history, atmosphere, company, whether it matches its surroundings or not, noises
Consider everything. Sounds, smells, even a disquieting proportion. A creaking, groaning, filthy ramshackle old house may immediately come to mind. But you could also have an antisepticly clean, white maze of rooms with no windows and the hum of automatic equipment. The flickering overhead lights may be making the characters jumpy, or the sound of quick footfalls with no one in sight. Maybe the floors don't seem quite level, even though a character sets a ball down and it doesn't roll away. Let your characters' reactions infect the reader.
I think verb choice when describing the features of a building are the best way to make it seem scary. Play around. I'm crap at this off my head but you know what I mean: vines crept, statues lurked etc
To make a building scary, especially a house, when you describe it, when anything happens in or near the house, don't ever use any words or descriptions that imply 'security'. A home is primarily intended to be a place of security. Take all the things away from a home that make it safe, and it becomes scary. Take away light, warmth, solidity. Take away quiet, peace and tranquility. It doesn't have to be gothic. Cold, dark and poorly maintained will do, if you describe it well.
Structurally weak buildings, and even buildings that give off that appearance. At 16, you'd never see me go into The Leaning Tower of Pisa.
I love all the ideas that are popping up and I suggest you use them. Meanwhile I had a few thoughts that initially came to my mind when I read the title: 1. Corners. Of course, you have them in just about any building except for a silo, so you can always use corners. It's not a unique feature, but something a good horror writer can utilize well, because anything can be hiding around them. This really goes along with what mammamia said about the writer being the scariest part (that is, the book is only as scary as the story it contains). 2. Claustrophobia. Again, there's something a bit off. 3. It's scarier if there's no way out. 4. It's also an old tool to get lost in a large structure. 5. It's scarier still if you're alone. Once I was at a dead end of a long hallway in a mall and I was all alone. Part of my imagination always created this living typhoon of fire spontaneously appearing and chasing me out of that dead end. Your mind does things when you're alone. 6. If something's there that makes you feel like you're being watched, all the better. The sensation that you're someone's prey is where the emotion of fear originated. If you have the feeling that the predator can come from anywhere, it's even scarier. Monosmith
Here are my ideas to make something scary: - Emptiness. This is the most important thing in my opinion. It makes it so it seems that something could jump out and there's no one around to help. - Flickering electric lights are always a nice touch. - Broken windows. - Some sort of repetitive out of the ordinary sound, like a chandelier swinging for seemingly no reason or a door banging open and closed. - There are certain surfaces that can actually freak people out. I'm not sure how you'd convey this through writing, but a certain tilt to a floor that people can't actually feel can do strange things to perception. Just my two cents.
